Thread: Mosfet Heating Circuits View Single Post

07-17-2010, 12:22 AM
 Harvey Gold Member Join Date: Jul 2009 Posts: 1,137
Quote:
 Originally Posted by Guruji Hi guys can you post the latest circuit for a 1000w or 2000w heater? Thanks
Hi Guruji,

The circuit is basically the same, but the voltage needs to be increased while keeping the amperage the same.

The IRFPG50 can tolerate upto 1000V before it goes into avalanche. As long as the current is kept at 6A, the MOSFET thermal dissipation will not change because the internal resistance of the MOSFET is always about 2 ohms when fully powered and the voltage drop across that will be the same for a given amperage.

So, the target configuration will be a 2kW heater at 6A and the necessary supply voltage for that power dissipation. The net impedance will need to be about 55.55 Ohms and the voltage will need to be about 333.33V.

So, let's imagine 6 of Glen's resistors in series and a 3kW power supply at 360V. This gives a practical current of 6A and 2.16kW of output power.

How do you get a 3KW supply?

Imagine if you had 10 of these in series: 36V 30AH V2.5 LiFePO4 Battery Pack

These batteries have a through current of 30A continuous and 2100W by themselves. So 10 gives you twenty one thousand watts of power available or the ability to run a 2kW heater for about 10 hours straight.

So the only real changes you need to make to Glen's Modified circuit is to ensure the electrical paths can handle the 6A and 360V. Of course the duty cycle is only about 50%, so the actual room heating from the dissipation will be half as far as true BTU's go and the actual battery drain will be 20 hours instead - maybe . . . it all depends on that aperiodicity - the real BTU's could be drastically less if the average dissipation is less than 50% depending on the integrated spike area and dissipation of that spike into the load.

EDIT: I made an error in those calcs - the battery capacity is 1200W not 2100W - you may wish to adjust my calcs accordingly.
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Last edited by Harvey; 07-17-2010 at 12:26 AM.